This invention relates to joints between optical cables each comprising a multiplicity of optical fibres.
It is the general practice to house protected splices or joints between optical fibres of two optical cables in a plurality of separately formed cassettes or other containers which are assembled together and housed in an overall joint enclosure into which the optical cables are fed, all such containers hereinafter, for convenience, being included in the generic term "cassette". Each cassette usually houses a plurality of protected optical fibre splices or joints and an excess length of each optical fibre of each splice or joint to provide for any necessity to re-splice or re-joint the optical fibres of any splice or joint which develops a fault.
By the expression "protected optical fibre splice or joint" is meant an optical fibre splice or joint which is surrounded by or enclosed within individual means for providing mechanical protection for the splice or joint.
In order to provide for an excess length of each optical fibre of the plurality of protected splices or joints housed within a cassette, it is common practice for a substantial length of optical fibre extending from a protected splice or joint to be coiled within the periphery of the cassette in at least one complete turn before the fibre emerges from the cassette. Furthermore, in order to avoid or limit the extent of optical signal attenuation and optical fibre fatigue that might otherwise be caused by a bend in an optical fibre, it is also common practice to ensure that the radius of the or each bend in the excess length of each optical fibre does not fall below a predetermined minimum value, usually in the order of 30 mm. As a consequence, the size of a cassette is determined, not by the number of protected optical fibre splices or joints which it houses, but by the minimum radius to which any optical fibre can be bent and a substantial proportion of the space within the cassette serves no useful purpose. Moreover, a plurality of such cassettes assembled together occupies a substantial volume with the consequential serious disadvantage that an overall optical cable joint enclosure which is to house one or more than one assembly of such cassettes is unnecessarily large and expensive and would occupy substantial space in a jointing bay or cabinet.